1. Field of the Invention
This invention relates to tubular steel sectional scaffolding which are widely used in the construction industry to serve as work platforms of varying heights for use by bricklayers, painters, carpenters, electricians and maintenance workers. The present invention relates to hoisting apparatus which is assembled to an end frame of the scaffold for hoisting sections of the next level of scaffold for assembly to the existing scaffold.
2. Description of the Prior Art
At the present time, there is no known hoisting equipment available for use in raising sectional scaffolding of the standard type used by craftsmen in the construction industry. The way that it is done today is that one worker remains on the ground, while a second worker is positioned in the top scaffold with a rope that is lowered to the ground so the ground worker may attach the end of the rope to a scaffold end frame or cross brace, so that the top worker pulls on the rope for raising the sections for assembly as the next level of scaffold. Very little work is done by the ground worker, and most of the heavy work is done by the top worker, who is standing on a top platform on top of the existing scaffold without any rails or supports for safety protection. The top worker may lose his balance and fall over the side, and the ground worker is helpless to give the top worker any assistance.
An early patent is the Brandt U.S. Pat. No. 1,539,109 which discloses an errecting crane and gin pull for use in erecting oil derricks. The erecting crane comprises a pair of generally vertical corner pipes, each provided with a pair of vertically-spaced arms having depending pins for pivotally engaging a pair of lugs of adjacent sleeve couplings on the lower sections of the derrick. The upper ends of the two pipes support a horizontal arm that carries a sheave or pulley and a lifting and lowering rope. This patent appears to be limited to use with derricks where the crane has supporting pipes that are mounted at the corner posts of the derrick.
The Cohen U.S. Pat. No. 2,377,758 discloses a boom or gib that is supported at the top of a standing scaffold for pivotal movement by means of a cable and winding drum that is positioned near ground level. The pivoted boom or gib is capable of being lowered for attachment to a preassembled scaffold at ground level, and then raising this entire preassembly up until it is attached to the existing standing scaffold. In other words, this patent bodily raises an entire new section of scaffold and connects it with a standing scaffold, rather than performing the assembly in sections.
The Jones U.S. Pat. No. 2,857,026 relates to means for erecting elevator towers. Such a tower is of the type that is used in handling building materials during the construction of a high-rise building. This elevator tower is not a simple scaffolding, but it is a double tower having two end frames and an intermediate frame which are reinforced by side braces. This patent has section hoist apparatus comprising a superstructure of two vertical posts, one attached to an end frame and the second attached to an intermediate frame. There is also a pivotally-mounted strut and a horizontal boom that is formed as an I-beam for accommodating a block and tackle apparatus. There is also a windlass located near ground level for use with a cable system for raising the sections of scaffolding.
The McDaniel et al U.S. Pat. No. 2,890,082 relates to tubular steel scaffolding which is provided with a hoisting apparatus for raising and lowering a lift platform for use in transporting various building materials. In other words, this hoisting apparatus is not for erecting the scaffolding itself, but merely to serve as an elevator means for raising building materials. There are two upper pulleys and two lower pulleys and a cable system that is tied into a hoisting unit near ground level.
The Copeland et al U.S. Pat. No. 3,504,461 relates to scaffold erecting equipment, but it is not a manual assembly apparatus, but rather it is a mobile unit of the forklift type having a vertically-extending structure forming a guide way for a carriage, together with power means for elevating and lowering the same. In other words, this Copeland patent relates to external power-operated means in complete modular sections, one on top of the other.